A cellular communication system has become the mainstream of mobile communication systems for mobile phones and the like. The cellular communication system covers a wide area that includes a plurality of areas (cells), each of which is a communication range of a base station. With this system, when a radio terminal moves between cells, the radio terminal switches between base stations so as to continue communication.
Today, the 3rd generation mobile telecommunication services based on a CDMA (Code Division Multiple Access) system, a W-CDMA (Wideband-CDMA) system, and the like are available. In the meantime, the next generation mobile telecommunication system that enables higher-speed communication has been extensively studied. In the 3rd Generation Partnership Project (3GPP), LTE-Advanced (LTE-A) is under study. LTE-A is an improved version of LTE which has been in use since around 2010 (see, for example, 3GPP TR25.913 V7.3.0 and 3GPP TR36.913 V8.0.1)
In recent years, with the spread of smartphones and the like, the characteristics of data handled in radio communication have become more diverse. In addition to conventional voice communication and browsing on the World Wide Web (WWW), the use of instant messaging (IM), social networking services (SNSs), and the like is increasing. Further, smartphones often perform data communication on IM and SNSs in background without being directly operated by the user.
In data communication on IM, SNSs, and the like using radio terminals such as smartphones, small-size data is intermittently transmitted and received. In the 3GPP, an effective method for handling these data communication characteristics different from those of the conventional voice communication and browsing on the WWW is being studied. In particular, how to perform intermittent transmission and reception of small-size data with low power consumption, without reducing the throughput, is being studied.
In the interval during which no data is exchanged, it is preferable that a radio terminal be switched to an RRC (Radio Resource Control) idle state (standby state).
However, intermittent data communication of small-size data involves frequent switching between an RRC connected state (communicating state) and an idle state. This results in an increased amount of RRC signaling and hence an increased power consumption.
For example, it is assumed that small packets are intermittently transmitted from a base station to a radio terminal. In this case, the radio terminal frequently switches between an RRC connected state (communicating state) and an idle state, so that the amount of RRC signaling increases. Therefore, the power consumed by the radio terminal increases.